TH2 questions. Please help

[tungym]

I get my TH2 and read their website dozen of times and still cannot get the meaning of:
1) DCP-differntial collective pitch-: does that mean an elevator stick input will only cause the 2 swashplates move up/down by different travel, or the 2 swashplate will also tilt forward (like a conventional single rotor helicopter)

2) The CH5 input: what is that about? the gyro shown on the "WIring Diagram" is suppose to stabalize the pitch (elevator). Why should the pitch stabalizing gyro connect to reciever CH5, instead of receiver elevator channel? So what actually receiver CH5 signal sending/receiving? Any mixing on the transmitter needed? Is CH5 actually sending the gyro sensitivity to the gyro? Any difference in connection/wiring if using 2 GY401( 2 spare signal gain CH needed?) rather than GY240?

3) Can TH2 applied in a fixed pitch tandem? Such that the pitch gyro controls the 2 throttle of the 2 motors rather than the DCP.

I can understand receiver Rudder channel connect to yaw gyro.

Totally confused !!
Please help !!

[tungym]

I re-read the TH2 funtioncal block diagram, for tandem heli, the DCP input should be elevator input, right.

So CH5 input is only for VTOL/ V22 like mode? Then where should be the pitch gyro connected to ...... to elevator receiver channel before going to TH2 ?

[v22chap]

1) DCP is there to help forward flight ( one swash up a little and one down ...just a little ) plus you also get a little forward / rear ward elevator cyclic mixed into that same elevator stick movement . And you can change that some by changing the constants in the program of tht TH-2 ..

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but Joes settings that you can download from his page and save to your puter and then install in the TH-2 are pretty well dialed in for what you need .
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2) Ch 5 is the input for the TH-2 's DCP so you can change the sensitivity of it at the TX ... and the gyro is augmenting that differentail collective to keep the birds pitch axis level and stable . Ch 5 is just a remote controll of that sensitivity


2 A ) Yes you do a mix in the TX from Master (elev) to slave (ch 5) of 70 , 70 to start out with ,,but this is used only to be able to set the gyro sensitivity at the field without taking off the body to get to the gyro sensitity .

A ) I don't think that using the 401 will make any difference ( just more money spent ,,but if you have it use it ) as if you " don't" hook up the remote gain wire it is always in HH which the elevator one is suppose to be in HH ,,but the rudder one is not suppose to be in HH ,, so the 401 won't work .

It also will not be good setting up the bird as you are suppose to put the elevator gyro in non heading hold and test hover it and play with the head linkage until it lifts off level and then put it in HH . But if you have enough RX channels to hook up the remote gain I guess it could work like a 240 .

3) I think guys have done this on non collective birds ..but I don't know exactly how.
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Pitch gyro input should connect to the Ch 5 of your RX , then the gyro's ouput to the TH-2 CH 5 input ( black single lead )

Your elevator TH -2 input lead (green ) is what hooks to the RX's elevator channel
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All of the DCP mixing is done inside the TH-2 ... the only mix needed is for the remote sensitity settings for the TX .

Hope this helps as I am staring to get confused too :roll: :wink: :oops:

[tungym]

Thanks vtolman,

Acording to the functional block diagram, one can assign either the elevator or CH5 as the source for DCP.

To my understanding, the pitch gyro is supposed to receive Elevator (recevier)input, such that the gyro can listen to elevator input to understand the pitch movement is done either by the pilot or by the wind.

But then, the if GY240 is connected to CH5, nowhere the GY240 can listen the elevator input!

I am using GY401 as I got 2 spare. Since it has a remote gain, am I supposed to connect it (as pitch gyro) to ELEV channel(TH2 setting DCP input from elevator) , while the GY401 sensitiy wire connect to a spare receiver channel (CH5).

I guess the TH2 setting of CH5->GY240-->DCP is cater for GY240, without the remote gain wire.

Am I right?

[v22chap]

Don't know what block diagram you are looking at but all mine show the TH -2's elevator (green wire ) going to the elevator channel on RX ,,not the gyro.

Ch 5 on the RX to the Ch 5 ( black wire on the TH -2 )

The Ch 5 on the TH -2 is DCP and has the collective and the elevator mixed thru this channel ... so the gyro plugged inbetween is seeing elevator signal

Page 11 of your pdf manual about middle page tells you to do this for the DCP gyro : Mount the DCP gyro onto the right side of the frame tube with double sided servo tape.Mount it as close a posssible to the CG .

The gyro INPUT connects to the RECIEVERS CH 5 output .. the gyro OUTPUT connects to the Th-2's CH5 input (black single wire ) not the green one ..

Just do it and it will work ...believe me ,,, you have to remember all the mixing and control is done inside the TH-2 ,,, and you can't think outside the box .......



Inputs/Outputs Description
The following table describes the purpose of the TH-2 inputs/outputs:
NameTypeDescription

Aileron input Aileron input from Rx or gyro

Elevator input Elevator input from Rx or gyro (THIS JUST TELLS YOU THAT IT CAN BE USED THIS WAY ,, NOT THAT IT SHOULD FOR THE TANDEM )

Rudder input Rudder input from Rx or gyro

CH5 input CH5 input from Rx or gyro

http://www.techmodelproducts.com/TH-2_manual_figures/TH-2_io.jpg

[tungym]

Thanks.

I finally got the answer from the TH2 manual point 13. Radio setup.

Actually , CH5 is programmed mixed with elevator channel on the "Transmitter". Now it make sense.
CH5 ATV 50/50
PMIX ELEV-->CH5 70/70

Strickly speaking, CH5 does not send gyro sensitivity/gain. It sends a mixed/proportion input to the pitch/DCP gyro.

[v22chap]

Now you got it ,,, kind of ,,, . like I said before ,,you can't think outside the box Joe did some tricky stuff here that most of us don't understand anthing about it .

[billyd]

My question is more basic. Which heli mode do you use in your transmitter? Obviously the TH2 does alot of the leg work. So what about the Tx? Joe says to turn off all mixing in the Tx, well in my radio (Futaba) the only way to do that (putting a really fine line on it) is to select a non-heli mode, because it will still have embedded mixes in the Tx depending on the swash type, if you choose a heli mode. Perhaps I should select h-1? I chose HR3 because that's a Trexx swash type, but maybe that's the problem. Help.

A second question. I downloaded the Twinn Rexx constants into the TH2 and tried running the electronics only and got alot of binding and such with the servo reversing all screwed up and possibly endpoint issues as well. Should I change the reversing in the Tx or the TH2? Maybe it doesn't matter. In fact it's so screwed up I'm not even sure where to begin. I had the servos all centered without the TH2 before hand. But maybe this goes back to question one as I am using Heli mode HR3. Perhaps that is the problem.

I am lost in the woods....:dontknow

[joe@tech-mp]

For Futaba use SWH1 = No TX mixing as specified in the manual. How hard can it be ? :) Do I need to produce a video ?



Joe

www.techmodelproducts.com

[tungym]

I set it right after playing with the TH-link software for 30 mins.

I plan to make a flybarless tandem and I take down all moving stuff between the swashplate and the central hub.

I get no binding anywhere.

I set the phase angle mechanically.

It would be nice if the TH2 can be program in real time as it is quite inconvenient to disconnect the USB and reconnect the battery to the BEC/ ESC.

I use FF7/T7CHP and set H-1 as swashplate type.

[billyd]

For Futaba use SWH1 = No TX mixing as specified in the manual. How hard can it be ? :) Do I need to produce a video ?



Joe

www.techmodelproducts.com (http://www.techmodelproducts.com)


I tend to overthink stuff.... or underthink it. :o

[billyd]

I set it right after playing with the TH-link software for 30 mins.

I plan to make a flybarless tandem and I take down all moving stuff between the swashplate and the central hub.

I get no binding anywhere.

I set the phase angle mechanically.

It would be nice if the TH2 can be program in real time as it is quite inconvenient to disconnect the USB and reconnect the battery to the BEC/ ESC.

I use FF7/T7CHP and set H-1 as swashplate type.


Thanks tungym. I agree it would be great to alter the parameters while running the software and the heli electronics simultaneously. I would guess that would be difficult/expensive to do ???

I'm sure my issues were do to setting my heli to HR3. I have to use H-1. I don't know what I was thinking. It was late and I should have stopped working on it and gone to bed. But I wanted to fire up the electronics and see how it all worked. But I knew I wasn't thinking clearly. I will give it another shot after work tonight.

[tungym]

ok, a bit out-topic..... just build my flybarless Trex450 based on TH2 with pitch/elevator gyro. A big success and will adopt the head to my flybarless twin-rex/ chinook soon.

I am still looking for some hollow main shaft to reduce weight on the chinook (no 3D on it anyway)

Remember all cyclic trim/centering must be done on TH2 (rather than on the Tx) , or you will loss a considerable degree of servo travel somehow.

http://www.helifreak.com/showthread.php?p=504378#post504378

[billyd]

That's pretty cool. I would want to go with 4 blades if I were to remove the flybar. That should improve aileron stability, but obviously alot more complex.

[tungym]

I am on my final stage of setting electronics on the TH2 for my "chinook"

Since I am hurry for a maiden on the coming weekend, I want to ask some fast questions:

1) I have not yet connected anything to the TH2 CH5 pin. When I pull the elevator Tx stick, the front swahplate tilt backward normally. However, at the rear swashplate, only the elevator servo moves downwards (swashplate tilted backward with some negative collective pitch movement as well). Is this normal.

2) If I plan to use GY401 on pitch control, should I connect receiver Elevator channel to GY401and receiver Ch5 to GY401 (gain wire). Then set TH2 to have DCP input from elevator?

Thanks

[tungym]

Just find a thread on a scratch built 1:35 model using TH2

http://www.rcgroups.com/forums/showthread.php?t=420932

[v22chap]

tungym
1) That don't sound right ... back cyclic servos all should move up / down in the back

2) DCP Ch 5 should hook to the gyro ,, Ch 5 RX should be hooked to TH -2 ch 5 (black wire if I remember right ), elevator should hook to RX elevator
Then you need to make a mix in your TX or the TH-2 between Elevator and CH-5 as the manual says

[tungym]

Thanks, I forget to set the mix and now it is ok.

Since I have a 6 channel receiver and I want to use one GY401, can I connect the DCP to elevator channel and spare the CH5 for the GY401 remote gain wire?

In the TH2 manual, DCP input can be connected from elevator channel. If so, I can spare one channel in the transmitter. Then will I lose the DCP proportion/ gain setting from the Transmitter?

Am I correct?

Thanks...

[v22chap]

Your assumption is correct as far as I know . I would for now just stay with the 240 as I think you will want the remote gain setting and I am not sure what hooking it up the other way will do to the TH-2's ability to read the mix either ;):shock:

You can hook up the 401 like you do a 240 ,,without the remote gain and it will work like a 240 if you happen to have a 401 and not the 240 in hand .. but I would opt for a bigger RX ...as you will soon want a bigger one anyhow ... for lights ,operating rear ramp , side door winch ,,,etc ..:lol::smokin::thumbup:

[joe@tech-mp]

tungym,

Yes, you can hook it up that way.

In that case, the gyro will be on both the elevator and DCP circuits. This may be ok for your application.

We found that having the gyro on just the DCP circuit proved to be the best solution. The bird flys much better. HH mode on elevator cyclic just dosen't work well from our testing.

Also, you lose the flexabilty to adjust the elevator/DCP ratio by adjusting your Tx (pmix of elevator to CH5).
This will then need to be done by adjusting the DCP gain constant in the TH-2 which requires a USB/PC connection.


Joe

www.techmodelproducts.com

[tungym]

Thanks Joe and V22chap. Now I understand the relation between DCP, Ch5 and elevator Ch mix.

I am rebuilding my front flybarless rotor back to flybar (as I later find that the TH2 cannot set the front/rear swash gain independently) before maiden.

Will Joe consider the next challenge of designing / building a V22 frame/ mechanism for us.

[v22chap]

Will Joe consider the next challenge of designing / building a V22 frame/ mechanism for us

It has been discussed ,,,but so far talk is all it has been ,,, have to completely get the Ch-47 done first . ;) :thumbup:

[Gra55h0pper]

Tungym,

One option you have to save a channel and still preserve the stability in the elevator plane is to "generate" the DCP channel on the heli, immediately after the receiver. The device I use for that is the Equalizer II, available from http://www.smart-fly.com. Setup is a bit cumbersome as you have to twiddle with the incr/decr buttons until the 2nd output (i.e. DCP) is (about) 30-60%% of the 1st (i.e. elevator). Just for setup, I used a servo to get this right, making sure that the servo deflection is the same from the Equalizer as it is (would be) from the receiver directly with the transmitter ATV set to 30-60% (I've got it at 50% now). When it is, the elevator channel from the receiver is fed into the Equalizer which then generates the elevator channel (unchanged) and the DCP channel. The DCP channel then feeds the gyro before going into the TH-2.

I'm still experimenting with it, but I think it'll work fine. I'll test-fly again this afternoon.

Just an idea...

H0pper.

[tungym]

Can someone share the % needed for yaw compensation. I found the yaw gyro has insufficient output to the rudder channel (I then increase the TH2 rudder gain and decrease the Tx ATV) , and I think its better to have compensation early than the gyro.

For rear CW rotor, should I add "right" yaw compensation?

[Gra55h0pper]

tungym - Have you resolved the rudder gyro issue you reported in the other thread? (with the 401 on which you left the gain input unconnected). The reason I'm asking is because I would recommend to only start adding yaw compensation when you've got no problems with yaw in hover anymore.
Note that on a tandem the torque of the rotors is completely cancelled out. This means that in a hover the gyro only has to apply small corrections. Even if you suddenly apply a lot of positive collective during hover, the helicopter should just go straight up without the tendency to pirouette (like in a tailrotor heli where the gyro then needs to "counter").
In case your Rexx wants to rotate around its axis during hover, then your problem is most likely that one of your swashplates tilts slightly left and the other slightly right thereby inducing yaw. If so, make sure to fix this by changing link lengths, not by applying rudder trim on the Tx.

In case your Rexx now hovers fine and you're referring to yaw compensation needed to correct for yaw induced by DCP (i.e. torque differences between the two rotors causing the torque to not completely be cancelled out) then you can fix it through elevator->rudder mixing either in the TH2, or in the Tx. You'll need to mix in right rudder when giving forward elevator (on a CW rear rotor). I believe this is a negative setting for the mix in the TH2.